NEW YORK (Reuters Health) - For couples struggling with
infertility, there are few lifestyle changes men can make to
improve the size and shape of their sperm, suggests a new study.

Sperm shape and size - known as morphology - were worse in
semen samples collected during summer months and from men who
smoked marijuana. Morphology was better among samples collected
after a man abstained from sexual activity for a few days.

But alcohol drinking and cigarette smoking were not
associated with misshapen sperm, researchers found. Neither was
a man's weight.

"It's always my recommendation to my patients to improve
their health as much as possible," Dr. James Smith said. "A
study like this doesn't discourage me from saying those things
to my patient."

Smith, who was not involved with the new study, is a male
reproductive health specialist at the University of California,
San Francisco.

It's believed that sperm with the most normal size and shape
are most likely to survive in the female reproductive tract,
Allan Pacey from the University of Sheffield in the UK and his
colleagues write in Human Reproduction. Little is known,
however, about the impact that certain lifestyle factors have on
sperm morphology.

To learn more, the researchers surveyed men who were seen at
one of 14 fertility clinics in the UK about their health and
lifestyle habits. They had information on 318 men with abnormal
sperm morphology and 1,652 men with normal sperm.

Men were considered to have abnormal sperm morphology if
less than four percent of their sperm in a sample of 200 was of
normal form, based on guidelines established by the World Health
Organization. Any count above four percent is considered normal.

The researchers found that men were about twice as likely to
have abnormal sperm if the sample was collected during the
summer. They were also more likely to have abnormal sperm if
they were young and smoked marijuana.

Although most other medical and lifestyle factors, such as
cigarette smoking and alcohol consumption, didn't seem to be
linked to sperm morphology, Smith said he still would advise his
patients to be as healthy as possible.

"Marijuana is certainly a potential worrisome risk factor
for hurting sperm quality," he said. "I'd tell my patients to
stop smoking marijuana. I wouldn't say to my patient to go out
and do whatever you want because it won't make a difference. To
me, that would be overstating those results."

The researchers also caution that the men included in the
study may not be representative of all couples with fertility
problems.

Smith said a better study would be to focus on whether the
couples went on to conceive a child.

"What would be great to see is if lifestyle factors - one
way or another - are going to be related to getting pregnant,"
he said.